This invention relates to the field of fluid and solids conditioning, and, more particularly to apparatus for handling and conditioning of particulate and gaseous material.
Materials handling of fluids and solids often involves conditioning steps. Such steps generally involve removing undesirable elements from a material stream by mechanical or chemical means. For example, drying involves removing excess fluid from solids and filtering involves removing unwanted material from a liquid or gas. Often particulate material is used to enhance the operation of the chemical or mechanical process.
One form of conditioning apparatus that is particularly useful is fluidizing apparatus that relies on vibration to fluidize particulate material. Once fluidized, the particulate material can be more easily processed by passing a gas, such as a drying gas, through the material and simultaneously conveyed to a new location. Alternatively, the fluidized particulate material may be used as a filter for treating the gas passing therethrough.
Fluidizing apparatus in the form of vibratory conveyors with gas drying are commonly used for simultaneously transporting and drying particulate material. Particulate materials handled in this manner vary widely and include, but are not limited to, wood fibers and wafers for panel boards, hog fuel for power boilers, dehydrated food stuffs and municipal waste and mill sludges. The degree of fluidization of the material is important to allow drying gas to pass through and circulate freely and continuously around individual particles of material. Such conveyors invariably have troughs or pans which are perforated to allow for free passage of drying gas through the material. In existing perforated trough conveyors , the degree of fluidization is dependent at least partly on the gas flow, and the retention time of the particulate material being conveyed is dependent upon the speed the material moves in the trough together with the length of the trough.
Applicant is the owner or co-owner of the following patents relating to fluidizing apparatus with gas processing:
U.S. Pat. No. 4,548,623 and Canadian Patent No. 1240918 entitled Perforated Trough Conditioning Device
U.S. Pat. No. 5,816,386 entitled Fluidizer Conveyor
U.S. Pat. No. 6,035,543 entitled xe2x80x9cJet Ventilated Conveyor Trayxe2x80x9d
Applicant is also the owner of co-pending U.S. patent application Ser. No. 09/119,306 filed Jul. 20, 1998 entitled xe2x80x9cInflatable Cushion Member for Helical Conveyorxe2x80x9d.
U.S. Pat. No. 4,548,623 to Naske is an example of a helical trough conditioning device for conditioning a fluid stream or a flow of granular solids using a gas. Helical trough conditioning apparatus, in which particulate material follows a continuous helical path about a central cylinder with gas circulating through the floor of the helical trough, is particularly useful for handling and drying of material as such conditioners are compact, rugged and efficient.
Other examples of conditioning apparatus known to applicant includes U.S. Pat. No. 3,742,614 to Bettermann et al., U.S. Pat. No. 4,237,622 to Francis, U.S. Pat. No. 4,970,806 to Hederer et al., U.S. Pat. No. 5,483,752 to Kreft et al., and U.S. Pat. Nos. 5,592,748 and 5,508,243 to Mitzkat et al.
In all types of conditioning apparatus, the goal is consistent and substantially complete treatment of the material undergoing conditioning. In the case of vibratory conditioning apparatus, vibration is required to fluidize and thoroughly mix the particulate material. Effective mixing may be inhibited if the particulate material contains unusually long or wide pieces which are difficult to fluidize. If the goal is drying of the particulate material, incomplete mixing of larger particles will tend to result in only partial drying of the larger pieces as all surfaces will not be equally exposed to the drying gas. If the goal is filtering of a gas by passing through fluidized particulate material, incomplete mixing of the larger particles will result in only partial removal of impurities as all the available reactive surfaces of larger particles may not be exposed to the gas. Therefore, it is desirable to expose the particulate material to additional mechanical action, such as tumbling, that ensures reliable mixing of larger particles.
To address the problem of proper mixing of particulate material, applicant has developed a new conditioning apparatus that is similar in construction to a helical trough conditioning device and therefore shares the desirable features of being compact, reliable and efficient. Instead of relying on a helical trough, however, the apparatus of the present invention uses a series of discrete, stacked annular troughs that communicate via passages between upper and lower troughs. Particulate material on the upper trough falls due to gravity through the passage to tumble and mix thoroughly on its journey to the lower trough. Mixing surfaces are provided in the passage to enhance the tumbling action. This promotes mixing and tends to ensure that all surfaces of the particulate material are exposed.
Accordingly, the present invention provides conditioning apparatus for handling particulate material comprising:
a central frame;
a plurality of spaced, annular troughs mounted to the central frame to support the particulate material, the troughs being arranged in a stacked configuration having successive pairs of upper and lower troughs with an uppermost trough for receiving the particulate material and a lowermost trough for discharging particulate material;
means for vibrating the plurality of troughs to fluidize and advance the particulate material in a first direction on each of the plurality of troughs;
a passage formed through each trough for particulate material to fall from the upper trough of a pair to the lower trough, the passage of the upper trough being non-aligned in a vertical plane with the passage of the lower trough such that particulate material falling from the upper trough is received on the lower trough to travel in the first direction over the distance of the lower trough before reaching the passage of the lower trough; and
a mixing surface in each passage to promote tumbling of the particulate material when falling through the passage.